ARGUMENTS

Tcl_Interp *interp (in/out) The interpreter in which
the ensemble is to be
created or found. Also
where error result
messages are written. The
functions whose names
start with
Tcl_GetEnsemble may have
a NULL for the interp,
but all other functions
must not.
const char *name (in) The name of the ensemble
command to be created.
Tcl_Namespace *namespacePtr (in) The namespace to which
the ensemble command is
to be bound, or NULL for
the current namespace.
int ensFlags (in) An ORed set of flag bits
describing the basic
configuration of the
ensemble. Currently only
one bit has meaning,
TCL_ENSEMBLE_PREFIX,
which is present when the
ensemble command should
also match unambiguous
prefixes of subcommands.
Tcl_Obj *cmdNameObj (in) A value holding the name
of the ensemble command
to look up.
int flags (in) An ORed set of flag bits
controlling the behavior
of Tcl_FindEnsemble.
Currently only
TCL_LEAVE_ERR_MSG is
supported.
Tcl_Command token (in) A normal command token
that refers to an
ensemble command, or
which you wish to use for
testing as an ensemble
command in
Tcl_IsEnsemble.
int *ensFlagsPtr (out) Pointer to a variable
into which to write the
current ensemble flag
bits; currently only the
bit TCL_ENSEMBLE_PREFIX
is defined.
Tcl_Obj *dictObj (in) A dictionary value to use
for the subcommand to
implementation command
prefix mapping dictionary
in the ensemble. May be
NULL if the mapping
dictionary is to be
removed.
Tcl_Obj **dictObjPtr (out) Pointer to a variable
into which to write the
current ensemble mapping
dictionary.
Tcl_Obj *listObj (in) A list value to use for
the list of formal pre-
subcommand parameters,
the defined list of
subcommands in the
dictionary or the unknown
subcommand handler
command prefix. May be
NULL if the subcommand
list or unknown handler
are to be removed.
Tcl_Obj **listObjPtr (out) Pointer to a variable
into which to write the
current list of formal
pre-subcommand
parameters, the defined
list of subcommands or
the current unknown
handler prefix.
Tcl_Namespace **namespacePtrPtr (out) Pointer to a variable
into which to write the
handle of the namespace
to which the ensemble is
bound.
______________________________________________________________________________

DESCRIPTION

An ensemble is a command, bound to some namespace, which consists of a
collection of subcommands implemented by other Tcl commands. The first
argument to the ensemble command is always interpreted as a selector
that states what subcommand to execute.
Ensembles are created using Tcl_CreateEnsemble, which takes four
arguments: the interpreter to work within, the name of the ensemble to
create, the namespace within the interpreter to bind the ensemble to,
and the default set of ensemble flags. The result of the function is
the command token for the ensemble, which may be used to further
configure the ensemble using the API described below in ENSEMBLEPROPERTIES.
Given the name of an ensemble command, the token for that command may
be retrieved using Tcl_FindEnsemble. If the given command name (in
cmdNameObj) does not refer to an ensemble command, the result of the
function is NULL and (if the TCL_LEAVE_ERR_MSG bit is set in flags) an
error message is left in the interpreter result.
A command token may be checked to see if it refers to an ensemble using
Tcl_IsEnsemble. This returns 1 if the token refers to an ensemble, or 0
otherwise.
ENSEMBLEPROPERTIES
Every ensemble has four read-write properties and a read-only property.
The properties are:
flags (read-write)
The set of flags for the ensemble, expressed as a bit-field.
Currently, the only public flag is TCL_ENSEMBLE_PREFIX which is
set when unambiguous prefixes of subcommands are permitted to be
resolved to implementations as well as exact matches. The flags
may be read and written using Tcl_GetEnsembleFlags and
Tcl_SetEnsembleFlags respectively. The result of both of those
functions is a Tcl result code (TCL_OK, or TCL_ERROR if the
token does not refer to an ensemble).
mappingdictionary (read-write)
A dictionary containing a mapping from subcommand names to lists
of words to use as a command prefix (replacing the first two
words of the command which are the ensemble command itself and
the subcommand name), or NULL if every subcommand is to be
mapped to the command with the same unqualified name in the
ensemble's bound namespace. Defaults to NULL. May be read and
written using Tcl_GetEnsembleMappingDict and
Tcl_SetEnsembleMappingDict respectively. The result of both of
those functions is a Tcl result code (TCL_OK, or TCL_ERROR if
the token does not refer to an ensemble) and the dictionary
obtained from Tcl_GetEnsembleMappingDict should always be
treated as immutable even if it is unshared. All command names
in prefixes set via Tcl_SetEnsembleMappingDict must be fully
qualified.
formalpre-subcommandparameterlist (read-write)
A list of formal parameter names (the names only being used when |
generating error messages) that come at invocation of the |
ensemble between the name of the ensemble and the subcommand |
argument. NULL (the default) is equivalent to the empty list. |
May be read and written using Tcl_GetEnsembleParameterList and |
Tcl_SetEnsembleParameterList respectively. The result of both of |
those functions is a Tcl result code (TCL_OK, or TCL_ERROR if |
the token does not refer to an ensemble) and the dictionary |
obtained from Tcl_GetEnsembleParameterList should always be |
treated as immutable even if it is unshared.
subcommandlist (read-write)
A list of all the subcommand names for the ensemble, or NULL if
this is to be derived from either the keys of the mapping
dictionary (see above) or (if that is also NULL) from the set of
commands exported by the bound namespace. May be read and
written using Tcl_GetEnsembleSubcommandList and
Tcl_SetEnsembleSubcommandList respectively. The result of both
of those functions is a Tcl result code (TCL_OK, or TCL_ERROR if
the token does not refer to an ensemble) and the list obtained
from Tcl_GetEnsembleSubcommandList should always be treated as
immutable even if it is unshared.
unknownsubcommandhandlercommandprefix (read-write)
A list of words to prepend on the front of any subcommand when
the subcommand is unknown to the ensemble (according to the
current prefix handling rule); see the namespaceensemble
command for more details. If NULL, the default behavior -
generate a suitable error message - will be used when an unknown
subcommand is encountered. May be read and written using
Tcl_GetEnsembleUnknownHandler and Tcl_SetEnsembleUnknownHandler
respectively. The result of both functions is a Tcl result code
(TCL_OK, or TCL_ERROR if the token does not refer to an
ensemble) and the list obtained from
Tcl_GetEnsembleUnknownHandler should always be treated as
immutable even if it is unshared.
boundnamespace (read-only)
The namespace to which the ensemble is bound; when the namespace
is deleted, so too will the ensemble, and this namespace is also
the namespace whose list of exported commands is used if both
the mapping dictionary and the subcommand list properties are
NULL. May be read using Tcl_GetEnsembleNamespace which returns a
Tcl result code (TCL_OK, or TCL_ERROR if the token does not
refer to an ensemble).